We've had the Republicans, here come the Democrats. Same set up as before - a sitting rather than standing debate (as Deadline USA's Alexander Belenky in the comments pointed out, making it a little less speechy) but this time the candidates are down to four. So it is Clinton v Obama v Edwards v Richardson. Read on for more ...

9pm: Let's open with what some still call the war on terror and threats to America; the hypothetical is posed that the US has hard evidence of a direct threat emerging from Pakistan. Obama is first up - he defends his assertion that the US could strike against al-Qaida in Pakistan. Edwards says if he was president and he knew where Bin Laden was he would act. He then pulls the hypothetical to the wider question of a nuclear-armed and not very stable Pakistan, arguing America should deal with short-term threats but lead a long-term initiative to rid the world of nuclear weapons.

9.10pm: Richardson's Pakistan policy would be to ask General Musharraf to step aside. Clinton plays a subliminal (perhaps it isn't) experience card. She talks about when a similar situation happened 10 years ago and a strike was authorised against a spot where Bin Laden was known to have been meeting. She then reels off a list of five things she would do to manage a crisis in Pakistan.

9.15pm: fleety3001 in the comments says Obama says hoarse. He does.

9.20pm: The candidates are asked what they would do the day after a nuclear bomb is detonated in an American city. Edwards says he act immediately because if the technology is out there it is a continuing threat, but a president must be calm and careful not to ratchet up the situation. Obama says the response to such a situation is something he has been working on. He talks about the need to rebuild the nuclear non-profileration treaty. Clinton also talks about prevention - increasing port security, etc. She then gets to the stateless terrorists who set off the bomb, and says nations who harbour such terrorists must understand the US will retaliate against them. (Yes, Bush said something similar in 2001.)

9.25pm: On to domestic issues. Clinton says everyone wants change but you don't get it by talking about it (she means you, Obama) or demanding it (and that's you, Edwards). She has been using the same line on the campaign trail of late.

Obama talks about healthcare - he says the Democrats all want similar systems but the difference between him and Clinton and Edwards is that he does not want the government to force people to take up insurance. He says his experience of meeting people is not that people do not want healthcare, it is that they can't afford it.

9.30pm: Clinton attacks Obama on his record, saying he has changed some of his positions since running for the Senate in 2004 - and it is wrong of him to accuse Edwards of changing his position on healthcare.

9.33pm: Edwards isn't won over - he says he and Obama have differences but they both speak up for change, which is why they came first and second in Iowa. The two look friendly and Edwards' references to attacks from the "status quo" appear to be references to Clinton ... now he names her, saying she only started attacking him and Obama when they started talking about change. Clinton retorts she is not running on a promise of change but 35 years of change.

9.37pm: Richardson asks "if experience is now a lepper" and goes through his resume as energy secretary, hostage negotiator, someone who has talked to North Korea, etc.

9.42pm: TheFirstCasualty in the comments notes the emerging Clinton-Richardson v Obama-Edwards battlelines. Interesting, as there was plenty of talk after Iowa of a Richardson-Obama deal. Richardson may not have liked that ...

9.45pm: Clinton wants to start bringing the troops home from Iraq within 60 days of entering the White House - but the end date is not specified. Richardson says he is running for president to bring the troops home within a year, so as better to concentrate on healthcare and education.

Obama says the bar for success in Iraq is set increasingly low and he opposed the war from the start. He explains his opposition to the Bush surge in terms of it having done nothing but bring violence in Iraq back to where it was two years ago. He calls for a "phased redeployment" of US troops.

9.50pm: More Clinton on Iraq - she wants to give notice to the Maliki government its "blank cheque" from the Bush admiration is over, but notes withdrawal is complicated and she would need to work on a plan with military chiefs.

10pm: The political director of ABC's local affiliate draws attention to the Richardson-Clinton line on the debate stage as an example of the the experience v change argument. He asks Clinton if it bothers her Obama is seen as more likeable. Clinton affects a look of hurt (it raises a chuckle in the audience)and says she doesn't want to answer that before, of course, she does. Clinton says America now has a president it wanted to have a beer with (is that a Bush-Obama parallel?) but what she can offer is experience. She also says that as a woman she would also represent change.

10.05pm: Obama talks about what his change would mean. He says he would work with Republicans to change the culture in Washington, cutting out those ever present "special interests" from legislation, and creating a new energy policy.

10.10pm: Richardson talks about his experience when asked if it is necessary for a president to have executive experience. Guess what? He then runs through his resume as energy secretary, being the only one on the stage who has negotiated with a foreign government, etc. Again. Luckily the moderator cuts him off. Richardson is then asked what he did as energy secretary. Good question.

The camera just cut to Clinton as it went to hear Edwards talk about how he has never taken a dime from a corporate lobbyist. She was smiling really really hard.

10.15pm: Clinton calls for a "reality break" to criticise the other candidates' talk that, she says, can't be made reality. First is a patient's bill of rights backed by Edwards in the Senate that never made it through the House of Representatives; second that while Obama attacks lobbyists his New Hampshire chair is a lobbyist. Obama shakes his head and mouths "that's not true" or something similar.

Her point appears to be getting things done and making change (yes, that word again) is hard and someone who has a CV similar to, say, Hillary Clinton is needed to get within a shot of it. Edwards say he will take on the lobbyists anyway.

10.20pm: Obama then turns up the change dial. He says you do not need to be cynical, there are times when America can change and a president can "inspire the American people to do better". He says the "American people can be mobilised around big changes, not incremental ones."

10.30pm: The debate is moving through policy discussions on carbon tax and tax cuts. Obama appears in control of the carbon tax brief, which is no doubt what he was aiming for. Edwards talks about tax cuts and job losses, saying college graduates and the middle class are suffering under current trend and fiscal policies. Obama promises an immediate sub-$75,000 tax cut to be funded by closing loopholes to balance the tax burden and put more money in middle class pockets.

10.35pm: Last question - what from the previous debates would the candidates wish they had never said? Richardson regrets saying his favourite supreme court justice was one he later learned had opposed Roe v Wade and civil rights; Edwards apologises to Clinton for being mean about one of her jackets, he tonight complements her on her appearance tonight. I couldn't quite catch the substance of Clinton and Obama's answers, but both were very consensual and said Democrats were better than Republicans.

Wrapping up: Who won? I really don't know. I think Obama. It wasn't the rhetorical Obama of Thursday night, but he was better than in his previous debates and maybe playing it safe works. Clinton did demonstrate experience. Was it enough? You decide - in the comments please. Not on Facebook.